Blender used by game designers?
No, Blender has not been used by any big game companies to create games, and no well-known games have been created with Blender. (Unless I missed them.)

However, as an experienced game developer myself, I can tell you that many have used Blender for 3D modelling, and exporting the models into other game development tools such as Unity to create games using their 3D models.

If you're thinking of getting into game development I would recommend you join gamedev.stackexchange.com, and perhaps start off with a couple of YouTube tutorials on how to use Blender and Unity (or other software) jointly.